Certain medicaments need to be formulated in so-called delayed-release or sustained release form.
Polyethylene oxide referred to as PEO below is moreover known as a component of medicaments in tablet form designed to be administered by oral route. This compound is marketed by the Union Carbide Corporation under the commercial name Polyox.RTM.. The use of PEO for formulating medicaments has furthermore been the subject matter of many earlier patents.
EP-A-0 277 092, in the name of Ciba-Geigy relates to a composition comprising a casing in a material that is porous to water but not to the active ingredient, surrounding a central core consisting of a mixture of a substance that is weakly soluble in water, and a hydrophilic swelling material, said material consisting of a mixture of PEO and a vinyl pyrrolidone/vinyl acetate polymer. The composition in that patent is an example of current compositions in which a core which swells when exposed to water is surrounded by a water-porous material, release of the active ingredient being delayed or sustained as a result of the time necessary to expand the core, and for diffusion to take place through the casing following the penetration of water.
The abstract of the U.S. Pat. No. 4,404,183 and U.S. Pat. No. 4,343,789 discloses two embodiments of a sustained release composition. In the first embodiment, the composition contains PEO, the active ingredient in an amorphous form, and a basic component. In the second embodiment, the active ingredient is nicardipine in an amorphous state, it being possible to omit the basic component.
Actually, the compositions according to the prior art are complex, require specific active ingredients or are provided in a specific form. Moreover, the results achieved are not always very good.